1. Field of the Invention
The present invention relates to a speaker apparatus, and in particular, to a speaker apparatus for reproducing a complicated waveform of low frequency such as a musical sound or the like with higher improved fidelity.
2. Description of the Related Art
Most conventional speaker apparatuses have a speaker housing having the shape of a box, a spherical shape or the like, and also have a speaker unit whose back surface is closed. In this case, sound waves radiating from the back surface of a diaphragm of the speaker unit are reflected by a wall surface of the speaker housing, and then, the reflected sound waves apply pressure to the back surface of the diaphragm of the speaker unit, to increase a reactance component of the acoustic impedance thereof. As a result, the sound pressure radiated from the front surface of the speaker unit changes according to frequencies, and phase characteristics are considerably disturbed. Then this leads to inhibition of high-fidelity reproduction.
Furthermore, in the conventional speaker apparatus having the box-shaped speaker housing, each surface of the speaker housing is prone to plate vibration. Additionally, a vibration mode is complicated due to reflection of vibration of corner surfaces. Thus, this leads to the occurrence of considerable noise. Consequently, the relationship among the relative times of element waveforms constitute, an original waveform which varies considerably. Therefore, reproducibility of the original waveform with higher improved fidelity is impaired.
In the speaker apparatus of the prior art, the speaker unit is fixed to the above-mentioned speaker housing having a box shape of a frame. In this situation, the vibration of a magnet cannot be suppressed. The vibration is transmitted to the housing through the frame and thus induces the plate vibration. This becomes a major factor of noise caused by the speaker housing. Moreover, the vibration transmitted to the speaker housing is again transmitted to the speaker unit through the frame and generates unnecessary vibration over the whole speaker unit. As a consequence, the transmitted vibration is superimposed onto the intrinsic vibration of the diaphragm, and consequently, the sound quality of the speaker apparatus is further deteriorated.
Furthermore, in the speaker apparatus of the prior art, the diaphragm of the speaker unit is located so as to face the listener. Therefore, the speaker apparatus of the prior art has such disadvantages that the speaker apparatus has sound waves having a high directivity and thus has a narrow coverage area. The speaker apparatus of the prior art having the directivity described above, has other disadvantages in so far as, the speaker apparatus has a narrow coverage area for reproducing a sound field space, and thus cannot obtain a satisfactory effect in a hall, a lobby or the like in which many people listen to the sound at the same time.
An essential objective of the present invention is therefore to provide a speaker apparatus which has less disturbance in the relative time relationship as compared with that of the prior art, which can reproduce a complicated waveform of low frequency such as a musical sound or the like with higher improved fidelity, and also has a wide coverage area for a sound field space.
In order to achieve the aforementioned objective, according to one aspect of the present invention, there is provided a speaker apparatus comprising:
a speaker unit including a magnet, a frame and a diaphragm, the speaker unit electromechanically transducing an input low-frequency signal into oscillation to oscillate the diaphragm, and to generate and radiate sound waves from the front surface of the diaphragm;
a speaker housing having a substantially cylindrical shape, the speaker housing having such a structure that the speaker unit is secured onto one end surface of the cylindrical shape of the speaker housing so as to substantially cover the speaker unit except for front and back surfaces of the diaphragm, and the speaker housing having an opening at another end surface of the cylindrical shape thereof;
a support bar extending and having one end secured to the back surface of the magnet of the speaker unit; and
a weight secured to another end of the support bar, the weight holding the support bar in a substantially vertical direction and grounding the magnet acoustically and virtually, thereby attenuating and suppressing oscillation transmitted from the magnet to the support bar.
According to another aspect of the present invention, there is provided a speaker apparatus comprising:
a speaker unit including a magnet, a frame and a diaphragm, the speaker unit electromechanically transducing an input low-frequency signal into oscillation to oscillate the diaphragm, and to generate and radiate sound waves from a front surface of the diaphragm;
a speaker housing having a substantially cylindrical shape, the speaker housing having such a structure that the speaker unit is secured onto one end surface of the cylindrical shape of the speaker housing so as to substantially cover the speaker unit except for front and back surfaces of the diaphragm, and the speaker housing having an opening in another end surface of the cylindrical shape thereof; and
support means having one end secured to the back surface of the magnet of the speaker unit, the support means supporting the speaker unit so as to hold the speaker unit in a substantially vertical direction.
In the above-mentioned speaker apparatus, the support bar and the weight are preferably formed by an integrated bar-shaped weight.
The above-mentioned speaker apparatus preferably further comprises a first cushioning member interposed between two parts of the support bar when dividing the support bar into two parts, the first cushioning member attenuating and suppressing oscillation transmitted from the magnet to the support bar.
Further, the above-mentioned speaker apparatus further comprises a second cushioning member interposed between the speaker unit and the speaker housing, the second cushioning member attenuating and suppressing oscillation transmitted from the speaker unit to the speaker housing.
In the above-mentioned speaker apparatus, the frame of the speaker unit preferably comprises a frame fitting part formed so as to be inclined from a vertical direction, and the second cushioning member is preferably formed so as to be fitted to the frame fitting part, inclined from the vertical direction and supporting the frame fitting part.
Further, in the above-mentioned speaker apparatus, the frame fitting part preferably comprises a plurality of projections which are used so as to be press-fitted into the second cushioning member.
Furthermore, the above-mentioned speaker apparatus further comprises an adaptive ring member interposed between the speaker unit and the second cushioning member, and having a shape adapted to receive and fix the frame of the speaker unit.
Still further, the above-mentioned speaker apparatus further comprises absorbing means for substantially absorbing the sound waves and limiting oscillation which are radiated and transmitted from the back surface of the diaphragm.
In the above-mentioned speaker apparatus, the speaker unit and the speaker housing are preferably formed so that the diameter of the frame of the speaker unit is substantially equal to the diameter of the cylinder of the speaker housing.
The above-mentioned speaker apparatus preferably further comprises diffusing means for, in the horizontal direction, substantially diffusing or reflecting the sound waves radiated from the front surface of the diaphragm.
In the above-mentioned speaker apparatus, the speaker housing preferably has either one of a cylindrical shape and an elliptical cylindrical shape.
According to the present invention, the speaker housing is cylindrical, and the weight is connected to the back surface of the magnet through the support bar secured to the back surface of the magnet. Thus, the reactance component of the acoustic impedance of the back surface of the speaker unit is reduced. Then, the impedance load can be substantially equal to the load of pure resistance. As a result, a high-quality reproduced sound, having less disturbance in the relative time relationship among element waveforms constituting a musical sound, can be obtained. Moreover, the speaker housing of the present invention is allowed to stand upright, and thus the front surface of the speaker unit is directed upward. Thus, horizontal directivity about the sound waves from the speaker unit can have an angle of 360 degrees. Therefore, the coverage area for listening can be greatly increased. In addition, reproducibility of the sound field space can be improved. Thus, a complicated waveform of low frequency such as a musical sound or the like can be reproduced with higher improved fidelity.